Milky Way gets a Makeover
Oh No
ASCII -- mjh]
(copy of press release)
Spiral galaxies are among the most beautiful and familiar objects in the
heavens, but a working explanation as to why galaxies evolve into
spirals has eluded astronomers for decades. Now, two independent
researchers have published a compelling solution to this eighty year old
problem, which appears in the November 2009 issue of Proceedings of the
Royal Society A. Consequently, the Milky Way must be remapped. This
newly emerging picture of our galaxy is being released online today as a
high-resolution digital image. The Milky Way is revealed as tightly
wound "grand design" two-armed spiral -- not a four-armed spiral as has
previously been supposed.
Download the new map of the Milky Way @
http://astrostudio.org/milkyway.html
Independent mathematician Charles Francis of Hastings, U.K., and
amateur astronomer Erik Anderson of Ashland, Oregon, had been working
on a quite different problem when the discovery was made. Anderson had
compiled data from existing sky surveys on more than 20,000 Milky Way
stars with accurately known positions and velocities. By treating orbits
as precessing ellipses, Francis found that mutual gravitation naturally
leads to orbital alignments that generate spiral patterns. Orbital
motions follow spiral arms over large distances.
Watch an animation of the galaxy in motion @ http://rqgravity.net/Spiral
Structure
Francis likens the gravitational potential of a spiral galaxy to a giant
funnel with spiral grooves. Stars, like rolling marbles, are channeled
along the grooves until they build enough momentum to escape. Escaping
stars migrate away from the galactic center, crossing over the next
highest groove, and falling back into the same groove they came from.
See the spiral funnel diagram @ http://rqgravity.net/images/spiralmotion
s/funnel2.gif
Francis and Anderson's model also explains why spiral patterns are
stable. As an arm accumulates stars, its gravitational field grows
stronger, making its "groove" deeper and drawing greater numbers of
stars into it. Thus, mutual gravity between stars reinforces spiral
structure. The gravity of the arms locks the rate of orbital precession
to spiral pattern speed (which rotates slowly backwards) for a wide
range of orbits. Interstellar gas, following similar motions, also
contributes to the formation of "grand
design" two-armed spirals.
"The idea is so simple that I had initially rejected it," Francis
confesses. "I thought that if it were right, it would already be known;
but when I compared it to data, it worked straight away, giving a
perfect fit."
Astronomer Rainer Klement, at the Max Planck Institute for Astronomy in
Heidelberg, Germany, agrees. "It is a very nice paper with very good
ideas and explanations for the kinematic structures we observe," Klement
remarks. "It comes up with an elegant way of explaining the velocity
distribution in the solar neighborhood." Klement believes that future
observations, covering even broader regions of the galaxy with even
greater precision, will support the paper's conclusions.
The introduction of a working model for spiral galaxies will
revolutionize the study of galactic dynamics. "It comes as a surprise to
most people that galactic orbits of stars are still treated in textbooks
using a model of epicycles introduced in the 1920s," Francis notes.
"Epicycles are generally believed to have been banished from astronomy
over three hundred years ago, when Newton explained Kepler's discovery
that planetary orbits are ellipses. In popular culture, 'adding
epicycles' refers to the process of introducing fudges to make a theory
fit data, when actually the theory needs to be replaced in its
entirety."
Learn about epicycles in modern astrophysics @
http://rqgravity.net/PtolemyIsDead
Regards
--
Charles Francis
moderator sci.physics.foundations.
charles (dot) e (dot) h (dot) francis (at) googlemail.com (remove spaces and
braces)